Electrically short antennas are well known in the art and comprise an antenna whose size is a small fraction of the wavelength with which it operates. Such antennas exhibit either an inductive or capacitive characteristic and are tuned to resonance by a reactance of the mutually opposite type. Its bandwidth of impedance matching, moreover, is subject to a fundamental limitation measured by its radiation and power factor which is proportional to its effective volume. These principles are reviewed and expanded together with a consideration of active antennas in an article entitled, "Small Antennas", by Harold A. Wheeler, which appeared in the IEEE Transactions On Antennas and Propagation, Vol. AP-23, No. 4, July, 1975, pp. 462-469.
In an airborne high frequency single sideband communication system where a resonant length antenna cannot be utilized due to aircraft size restraints, prior art practice typically involves the use of mechanically adjusted passive reactances together with RF amplification at a point remote from the antenna feedpoint.